Cemented fixation of an implant, mainly used for osteoporotic bone, requires bone cement to hold the implant in place. Although considerable advances have already been made to improve the biological performance of cement, the ideal long-term mechanical stability of a cemented implant is still not achieved. An ideal cementing material for cemented surgeries should have surface energy and mechanical interlock to ensure a long-lasting fixation between implant-cement and cement-bone interfaces. The critical task for creating a long lasting tissue-implant interface resides in achieving the functional integration to mimic native tissue-tissue failure response. Appropriate mechanical interlock and adequate osseointegration is present between the joining tissues at natural tissue-tissue interfaces. Since bone cement is a bio-inert material, in case of natural tissue-cement interface in cemented joint, the joining of cement with bone is done by mechanical interlock. The goal of this innovation is to increase the osseointegration at the tissue-cement interface by improving the bioactivity of cement so that it will mimic native tissue-tissue failure response under functional loading.
The debonding of the PolyMethylMethAcrylate (PMMA) cement from bone in cemented joint replacement is frequently reported in literature. In the case of total cemented joint replacements, implant loosening occurs due to debonding of the bone-cement interface due to poor osseointegration of bone cement with bone or weakening of bone due to local high stressed area. Heterogeneous flow of bone cement around the implants due to the porosity of trabecular bone has been observed. Localized fractures may occur at the narrow confined tissue-cement interface by a relatively smaller force in compare to failure force of bone due to this heterogeneous flow of cement (FIG. 1). PMMA is a bio-inert material. Current trend of biomaterial research is focused on the addition of bio-additives with cement to solve the debonding problem by improving the osseointegration of cements with bone. The purpose of this innovation is to coat PMMA at the bone/cement interface by nanofiber immobilized with drugs to improve the biocompatibility PMMA cement without the diminishing the mechanical properties of PMMA at in vivo condition.
Nanofibers are a simple, scalable, inexpensive and supplementary surface treatment technique for biomaterials that have been implemented by various researchers. Most of research of the nanofiber applications on cement is focused on improving the mechanical properties of cement rather than improving the bioactivity of bone cement. For example, Wagner and Cohn used high performance polyethylene fibers as a reinforcing phase in PMMA bone cement. The authors found that the surface coating treatments of the Spectra 900 polyethylene fibers apparently did not significantly affect the mechanical properties of the PMMA bone cement. Saha and Pal found that addition of 1-2% by weight of graphite and up to 6% aramid fibers into PMMA cement reinforced significantly the mechanical strength of PMMA. However, the previous authors did not conduct cell viability studies to evaluate the effect of their fiber treatments on the biocompatibility of PMMA. Nanofibers can be biomineralised by immobilization of functional proteins and minerals with the fiber. Wu. et al. produced aligned poly(1-lactide)/poly(methyl methacrylate) binary blend fibers and mats loaded with a chimeric green fluorescence protein having a bioactive peptide with hydroxyapatite binding and mineralization property by pressurized gyration. The previous authors' research showed that nanofiber can have controllable inherent mineralization abilities through integrated bioactivity. However, no method has been proposed by which to apply nanofiber membrane on cement to improve its biomechanical properties. In our research, we showed a technique to put the electrospun fiber membrane on the surface of set PMMA cement. Our recent research manuscript in Nanomaterial Journal titled “Use of Polycaprolactone Electrospun Nanofibers as a Coating for Poly (methylmethacrylate) Bone Cement” showed how to apply fiber membrane on cement for biomechanical characterization (FIG. 2). But the problem is how a clinician is going to apply such fiber membrane in real life for cemented surgeries. The rationale for using bone cement is that it is injected in the dough phase of mechanical properties during the polymerisation process. It is used as “grout” so a space filler to give either an interference fit between the implant and the supporting bone or to fill defects such as when it is used for cemented joint surgeries. In our innovation, we have developed and described a process by which the nanofiber membrane of any specific size or shape, with or without drugs can be placed on the surface of set cement. Our invented technique can also control the flow of cement into bone cavities using the flexibility and strength of electrospun nanofiber membrane.